The amount of ejaculate released changes all the time. If a person with a penis goes a few days without sex or masturbation , they’re likely to ejaculate more. And vice versa if you masturbate often within a short period it can be reduced.
Factors like smoking, diet , genetics and overall health can also impact the amount of semen and ejaculate. Age is also a big factor. Those with a penis produce the most semen in their early 30s. Maintaining hydration can also assist.